Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
xy=[(1,0),(-1,0),(0,1),(0,-1)]
ans=chk=0
h,w=map(int,input().split())
d=[[0]*w for i in range(h)]
l=[]
for i in range(h):
    a=input()
    chk+=a.count("#")
    l.append(a)
p=set([(0,0)])
while len(p):
    a,b=p.pop()
    for y,x in xy:
        y+=a
        x+=b
        if 0<=y<h and 0<=x<w and l[y][x]!="#":
            if d[y][x]==0 or d[y][x]>d[a][b]+1:
                d[y][x]=d[a][b]+1
                p.add((y,x))

print(-1 if d[h-1][w-1]==0 else h*w-1-chk-d[h-1][w-1])